Schrodinger's Poor Cat

maybe the fleas couldnt smell or hear and same with the cat.

ok dude, you're not a physicist as well but you're worse, by observing we don't mean using one or other sense, but any possible experiencing mechanism, so in the case that certain observer couldn't use any sense and not experience the event in any possible way, well, that thing is not an observer and with a little intuition you can realize that if it ever was alive now its as fucking dead as your brain... naw just kidding

but what if nothing was able to observe anything in the whold world, then would everything be in a state of superposition?

well, think about it, if nothing were able to observe anything in the universe then there is no consciousness anywhere in the universe and here is where this turns to the philosophical basis of quantum mechanics.

Yes i think everything would be in a state of superposition and although this might seem illogical think about it, for the last 150 years we've been discovering shocking things that have completely torn down our common sense, and it's just because the complexity of existence 'happens' to be much more complicated than the small part of it we're able to experience

that's right you're not a physicist... see the cat fleas and shit are considered to be a single particle, so the superposition principle still holds. Either the system is affected or not, but the effect is directly related to a quantum event so it doesn't matter if there are fleas mosquitos or your mama, you see